1. Field of the Invention
The present invention relates to an automatic transmission for vehicles, and more particularly, to a planetary gear train of an automatic transmission for vehicles capable of reducing the whole length to improve mounting property and improving power transfer performance to reduce fuel costs.
2. Description of the Related Art
Typically, a multi-level transmission mechanism of an automatic transmission is implemented by a combination of a plurality of planetary gear sets and friction elements, and since the more the implementable shift stages are, the more possible a design of more proper shift ratios and an excellent vehicle in the light of power performance and fuel efficiency may be implemented, an untiring research into a planetary gear train for an automatic transmission capable of implementing more shift stages has been made.
Since the above-mentioned planetary gear train has different durability, power transfer efficiencies, sizes, or the like depending on a connection structure of rotation elements (a sun gear, a planetary gear, a ring gear, etc) even though it implements the same shift stage, research and development for manufacturing the planetary gear train which is stronger, has no power loss, and is compact have been continued.
In addition, the planetary gear train implements a plurality of shift stages, and in the light of a shift control, whether or not the planetary gear train satisfies an operation condition when performing a sequential shift as a neighboring shift stage and whether or not an inter-stage ratio between neighboring shift stages is implemented at a proper level are magnified as one of differentiated functions.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.